The disclosure relates to a sensor unit for a vehicle and to a method for producing a sensor unit for a vehicle.
Present-day rotational speed sensors are constructed by means of connecting in an electrical manner an ASIC package that is based on a leadframe to a two-core connection cable. The customer-specific application in the vehicle and also the insulation of the electrical components are generally achieved in a simple or modular form by means of an injection molding process using a thermoplastic or duroplastic material. The connection cable and components for application in the vehicle and plug connector are manufactured on separate production lines. As a result of this manufacturing procedure, it is consequently generally necessary to provide a production line for manufacturing the leads and a costly production line for manufacturing the sensor and also to provide transportation concepts between the two production lines.
In the case of the injection molding process, the ASIC package or the sensor circuit is generally fixed by means of a retaining unit. The sealing arrangement between the retaining unit and the injection molding is provided by means of ribs that have small dimensions and fuse on as a result of the temperature during an injecting process and thus ensure a particular shape and a material closure. The sealing arrangement between the connection cable and the injection molding is performed by means of a mixture formed by activating the interfacial adhesive layers (slightly fusing on) and shrinking on the injection molding during the cooling process. The electrical connection between the leadframes of the ASIC package and the connection cable is usually performed by means of laser soldering, crimping with the aid of a terminal or by crimp connections and also direct welding the individual leads of the connection cable to the leadframe. The present-day construction is encumbered by considerable disadvantages of long cycle times caused as a result of the heavy shot weight of the synthetic material (cooling down times) and also the great variety of retaining and injection molding tools that are necessary for the different vehicle applications. Furthermore, depending upon the customer's application or the installation requirements of the sensor unit in the vehicle, the thermoplastic injection molding of the sensor circuit in different dimensions requires in the case of every new variant a substantial approval expenditure for the design and approval process since the thermal and mechanical stresses in the case of the injection molding process on the sensor circuit are to be avoided.
DE 10 2005 012 709 A1 discloses by way of example a magnetic field sensor, in particular a rotational speed sensor and/or direction of rotation sensor for a vehicle wheel or for the drive train of a vehicle. The magnetic field sensor comprises a retaining element for a sensor element and where necessary for further sensor components. The retaining element is embodied as an injection molding and comprises a pocket-like recess in the region of its read-side end face in which the sensor element is supported during the subsequent injection molding process with synthetic material at least in the direction of the injection pressure and thus is protected against mechanical damage. A connection arrangement for the described magnetic field sensor comprises a connection element that comprises two connection pieces in a first contact-making region and said connection pieces are connected respectively by way of a crimp connection in an electrical and mechanical manner to the connection cable ends that have been stripped of insulation. In a second contact-making region, the connection pieces can be connected in an electrical and mechanical manner to connection leads of a sensor element. The connection element is encased at least in part by a synthetic material injection molding that comprises a window-shaped cutout in a transition region between the first contact-making region and the second contact-making region, said window-shaped cutout being sealed during the process of injection molding the synthetic material injection molding in the injection molding tool. These connection pieces are initially embodied in one piece so as to facilitate the positioning of the connection element prior to the injection molding process and said connection pieces are subsequently electrically insulated with respect to one another by means of separating the connecting parts.
DE 10 2006 029 980 A1 discloses an exemplary sensor arrangement, in particular a sensor arrangement for sensing the rotational speed and/or direction of rotation for a vehicle wheel or for the drive train of a vehicle. The sensor arrangement comprises a retaining element, at least one sensor element, which is arranged on the retaining element and comprises a connector, wherein the connector is connected in an electrical manner at at least one connecting site by way of corresponding connecting means to at least one lead of a connection cable. The ends of the connection cable that have been stripped of insulation can be connected by way of example in each case by means of a crimp connection in an electrical manner to the connecting means. The end of the at least one lead of the connection cable is embedded with the connecting means at least in part in the retaining element so that a preform is produced, wherein the at least one connecting site is recessed for connecting to the sensor element. After contact has been made with the sensor element, the retaining element together with the sensor element can be injection molded with a synthetic material sheath.